On-line partial discharge measurement of turbine generators with new noise rejection techniques on pulse-by-pulse basis

Online partial discharge tests for turbine generators are useful for recognizing abnormal or deteriorated stator winding insulation without a machine outage. One problem related to such a test is additional installation of sensors and their reliability. The authors propose that wires of a resistance temperature detector (RTD) embedded in a stator slot be applied as a partial discharge sensor in the form of an RF coupler. The other problem is electrical noise that is a pulse similar to partial discharge in frequency characteristic and has higher amplitude than partial discharge. The authors have developed an online partial discharge monitor for turbine generators with three noise rejection techniques on a pulse-by-pulse basis. The first is founded on the correlation between pulse height in two frequency bands. The second is based on the correlation between pulse height from the two partial discharge sensors. The last is noise gating. It was found that most noise pulses were successfully rejected with the monitor under trial conditions